Designation D4632/D4632M − 15a Standard Test Method for Grab Breaking Load and Elongation of Geotextiles1 This standard is issued under the fixed designation D4632/D4632M; the number immediately follo[.]
Trang 1Designation: D4632/D4632M−15a
Standard Test Method for
This standard is issued under the fixed designation D4632/D4632M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision A number in parentheses indicates the year of last
reapproval A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S Department of Defense.
1 Scope
1.1 This test method is an index test which provides a
procedure for determining the breaking load (grab strength)
and elongation (grab elongation) of geotextiles using the grab
method This test method is not suitable for knitted fabrics and
alternate test methods should be used While useful for quality
control and acceptance testing for a specific fabric structure,
the results can only be used comparatively between fabrics
with very similar structures, because each different fabric
structure performs in a unique and characteristic manner in this
test The grab test methods does not provide all the information
needed for all design applications and other test methods
should be used
1.2 Procedures for measuring the breaking load and
elon-gation by the grab method in both the dry and wet state are
included; however, testing is normally done in the dry
condi-tion unless specified otherwise in an agreement or
specifica-tion
1.3 The values stated in either SI units or inch-pound units
are to be regarded separately as standard The values stated in
each system may not be exact equivalents; therefore, each
system shall be used independently of the other Combining
values from the two systems may result in non-conformance
with the standard
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use It is the
responsibility of the user of this standard to establish
appro-priate safety and health practices and determine the
applica-bility of regulatory limitations prior to use.
2 Referenced Documents
2.1 ASTM Standards:2
D76/D76MSpecification for Tensile Testing Machines for Textiles
D123Terminology Relating to Textiles
D1776/D1776MPractice for Conditioning and Testing Tex-tiles
D2905Practice for Statements on Number of Specimens for Textiles(Withdrawn 2008)3
D4354Practice for Sampling of Geosynthetics and Rolled Erosion Control Products(RECPs) for Testing
D4439Terminology for Geosynthetics
E177Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3 Terminology
3.1 Definitions:
3.1.1 atmosphere for testing geotextiles, n—air maintained
at a relative humidity of 65 6 5 % relative humidity and temperature of 21 6 2°C [70 6 4°F]
3.1.2 breaking load, n—the maximum force applied to a
specimen in a tensile test carried to rupture
3.1.3 cross-machine direction, n—the direction in the plane
of the fabric perpendicular to the direction of manufacture
3.1.4 elongation at break, n—the elongation corresponding
to the breaking load, that is, the maximum load
3.1.5 geotextile, n—any permeable textile material used
with foundation, soil, rock, earth, or any other geotechnical material, as an integral part of a man-made product, structure,
or system
3.1.6 grab test, n—in fabric testing, a tension test in which
only a part of the width of the specimen is gripped in the clamps
3.1.6.1 Discussion—For example, if the specimen width is
101.6 mm [4 in.] and the width of the jaw faces 25.4
mm [1 in.], the specimen is gripped centrally in the clamps
3.1.7 machine direction, n—the direction in the plane of the
fabric parallel to the direction of manufacture
1 This test method is under the jurisdiction of ASTM Committee D35 on
Geosynthetics and is the direct responsibility of Subcommittee D35.01 on
Mechani-cal Properties.
Current edition approved May 15, 2015 Published June 2015 Originally
approved in 1991 Last previous edition approved in 2015 as D4632/D4632M–15.
DOI: 10.1520/D4632_D4632M-15A.
2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3 The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 United States
Trang 23.1.8 For definitions of other terms used in this test method,
refer to TerminologyD123or Terminology D4439
4 Summary of Test Method
4.1 A continually increasing load is applied longitudinally
to the specimen and the test is carried to rupture Values for the
breaking load and elongation of the test specimen are obtained
from machine scales or dials, autographic recording charts, or
interfaced computers
5 Significance and Use
5.1 The grab method is applicable whenever it is desired to
determine the “effective strength” of the fabric in use, that is,
the strength of the material in a specific width, together with
the additional strength contributed by adjacent material There
is no simple relationship between grab tests and strip tests since
the amount of fabric assistance depends on the construction of
the fabric It is useful as a quality control or acceptance test
5.2 The procedure in Test Method D4632/D4632M for the
determination of grab strength of geotextiles may be used for
acceptance testing of commercial shipments, but caution is
advised since information about between-laboratory precision
is incomplete Comparative tests as directed in 5.2.1 are
advisable
5.2.1 In case of a dispute arising from differences in
reported test results when using the procedures in Test Method
D4632/D4632M for acceptance testing of commercial
shipments, the purchaser and the manufacturer should conduct
comparative tests to determine if there is a statistical bias
between their laboratories Competent statistical assistance is
recommended for the investigation of bias As a minimum, the
two parties should take a group of test specimens that are as
homogeneous as possible and which are from a lot of material
of the type in question The test specimens should then be
randomly assigned in equal numbers to each laboratory for
testing The average results from the two laboratories should be
compared using the appropriate Student’s t-test and an
accept-able probability level chosen by the two parties before testing
is begun If a bias is found, either its cause must be found and
corrected or the purchaser and the manufacturer must agree to
interpret future test results in the light of the known bias
5.3 Most geotextile fabrics can be tested by this test method
Some modification of clamping techniques may be necessary
for a given fabric, depending upon its structure Special
adaptation may be necessary with strong fabrics, or fabrics
made from glass fibers, to prevent them from slipping in the
clamps or being damaged as a result of being gripped in the
clamps, such as cushioning the clamp or boarding the specimen
within the clamp
5.4 This test method is applicable for testing fabrics either
dry or wet It may be used with constant-rate-of-traverse (CRT)
or constant-rate-of-extension (CRE) type tension machines
However, there may be no overall correlation between the
results obtained with the CRT machine and the CRE machine
Consequently, these two tension testers cannot be used
inter-changeably In case of controversy, the CRE machine shall
prevail
6 Apparatus
6.1 Tensile Testing Machine, of the
constant-rate-of-extension (CRE) or constant-rate-of-traverse (CRT) type with autographic recorder conforming to the requirements of Speci-ficationD76/D76M
6.2 Clamps, having all gripping surfaces parallel, flat, and
capable of preventing slipping of the specimen during a test Each clamp shall have one jaw face measuring 25.4 by 50.8
mm [1 by 2 in.], with the longer dimension parallel to the direction of application of the load The other jaw face of each clamp shall be at least as large as its mate Each jaw face shall
be in line, both with respect to its mate in the same clamp and
to the corresponding jaw of the other clamp
7 Sampling and Selection
7.1 Division into Lots and Lot Samples—Divide the material
into lots and take a lot sample as directed in PracticeD4354 Rolls of fabric are the primary sampling unit
7.2 Laboratory Sample—Take for the laboratory sample a
swatch extending the width of the fabric and approximately
1 m [39.37 in.] along the selvage from each roll in the lot sample The swatch may be taken from the end portion of a roll provided there is no evidence that it is distorted or different from other portions of the roll In cases of dispute, take a swatch that will exclude fabric from the outer wrap of the roll
or the inner wrap around the core
7.3 Test Specimens—Cut the number of specimens from
each swatch in the laboratory sample determined as directed in Section8 Take no specimens nearer the selvage of fabric edge than1⁄20of the fabric width or 150 mm [6 in.], whichever is the smaller Cut rectangular specimens 101.6 by 203.2
mm [4 by 8 in.] Cut the specimens to be used for grab tests in the machine direction with the longer dimension parallel to the machine direction and the specimens to be used for grab tests
in the cross-machine direction with the longer dimension parallel to the cross-machine direction Locate each group of specimens along a diagonal line on the swatch so that each specimen will contain different warp ends and filling picks Draw a line 37 mm [1.5 in.] from the edge of the specimen running its full length For woven and reinforced nonwoven fabrics, this line must be accurately parallel to the lengthwise yarns in the specimen
8 Number of Specimens
8.1 Unless otherwise agreed upon as when provided in an applicable material specification, take a number of test speci-mens per swatch in the laboratory sample such that the user may expect at the 95 % probability level that the test result is
no more than 5 % above the true average for each swatch in the laboratory sample for each the machine and cross-machine direction, respectively
8.1.1 Reliable Estimate of v—When there is a reliable estimate of v based upon extensive past records for similar
materials tested in the user’s laboratory as directed in the method, calculate the required number of specimens usingEq
1, as follows:
Trang 3n = number of test specimens (rounded upward to a whole
number),
v = reliable estimate of the coefficient of variation of
indi-vidual observations on similar materials in the user’s
laboratory under conditions of single-operator
precision, %,
t = the value of Student’s t for one-sided limits (see Table
1), a 95 % probability level, and the degrees of freedom
associated with the estimate of v, and
A = 5.0 % of the average, the value of the allowable
variation
8.1.2 No Reliable Estimate of v—When there is no reliable
estimate of v for the user’s laboratory,Eq 1should not be used
directly Instead, specify the fixed number of 10 specimens for
the machine direction tests and 10 specimens for the
cross-machine direction tests The number of specimens is calculated
using v = 9.5 % of the average for both machine direction and
cross-machine direction These values for v are somewhat
larger than usually found in practice When a reliable estimate
of v for the user’s laboratory becomes available, Eq 1 will
usually require fewer than the fixed number of specimens
9 Conditioning
9.1 Bring the specimens to moisture equilibrium in the
atmosphere for testing geotextiles Equilibrium is considered to
have been reached when the increase in mass of the specimen
in successive weighings made at intervals of not less than 2 h
does not exceed 0.1 % of the mass of the specimen In general
practice, the industry approaches equilibrium from the “as
received” side
N OTE 1—It is recognized that in practice geotextile materials are
frequently not weighed to determine when moisture equilibrium has been
reached While such a procedure cannot be accepted in cases of dispute,
it may be sufficient in routine testing to expose the material to the standard
atmosphere for testing for a reasonable period of time before the
specimens are tested A time of at least 24 h has been found acceptable in
most cases However, certain fibers may exhibit slow moisture
equaliza-tion rates from the “as received” wet side When this is known, a
preconditioning cycle, as described in Practice D1776/D1776M , may be
agreed upon between contractual parties.
9.2 Specimens to be tested in the wet condition shall be immersed in water maintained at a temperature of 21 6 2°C [70 6 4°F] The time of immersion must be sufficient to wet-out the specimens thoroughly, as indicated by no signifi-cant change in strength or elongation following a longer period
of immersion, and at least 2 min To obtain thorough wetting,
it may be necessary or advisable to add not more than 0.05 %
of a nonionic neutral wetting agent to the water
10 Procedure
10.1 Test the conditioned specimens in the standard atmo-sphere for testing in accordance with Section9
10.2 Set the distance between the clamps at the start of the test at 75 6 1 mm [3 6 0.05 in.] Select the load range of the testing machine such that the maximum load occurs between
10 and 90 % of full-scale load Set the machine to operate at a speed of 300 6 10 mm/min [12 6 0.5 in./min]
10.3 Secure the specimen in the clamps of the testing machine, taking care that the long dimension is as nearly as possible parallel to the direction of application of the load Be sure that the tension in the specimen is uniform across the clamped width Insert the specimen in the clamps so that approximately the same length of fabric extends beyond the jaw at each end Locate the jaws centrally in the widthwise direction by having the line which was drawn 37 mm [1.5 in.] from the edge of the specimen run adjacent to the side of the upper and lower front jaws which are nearest this edge This ensures that the same lengthwise yarns are gripped in both clamps
10.4 If a specimen slips in the jaws, breaks at the edge of or
in the jaws, or if for any reason attributed to a faulty operation the result falls markedly below the average for the set of specimens, discard the result and take another specimen Continue this procedure until the required number of accept-able breaks have been obtained
N OTE 2—The decision to discard a break shall be based on observation
of the specimen during the test and upon the inherent variability of the fabric In the absence of other criteria for rejecting a so-called jaw break, any break occurring within 5 mm [ 1 ⁄ 4 in.] of the jaws which results in a value below 80 % of the average of all the other breaks shall be discarded.
No other break shall be discarded unless it is known to be faulty.
N OTE 3—It is difficult to determine the precise reason for breakage of test specimens near the edge of the jaws If breaks are caused by damage
to the specimen by the jaws, then the results should be discarded If, however, they are merely due to randomly distributed weak places in specimens, the results should be considered perfectly legitimate In some cases, breaks may be caused by a concentration of stress in the area adjacent to the jaws If this occurs, the specimen is prevented from contracting in width as the load is applied In such cases, a break near the edge of the jaws is inevitable and shall be accepted as a characteristic of the geotextile when tested by this test method.
10.5 Start the tensile testing machine and the area measur-ing device, if used, and continue runnmeasur-ing the test to rupture Stop the machine and reset to the initial gage position Record and report the test results for each direction separately 10.6 If fabric manifests slippage in the jaws, the jaw faces, but not the jaw dimensions, may be modified If a modification
is used, the method of modification should be stated in the report
TABLE 1 Values of Student’s t for One-Sided Limits
and the 95 % ProbabilityA
One-Sided
One-Sided
One-sided
AValues in this table were calculated using Hewlett Packard HP 67/97 Users’
Library Programs 03848D, “One-Sided and Two-Sided Critical Values of
Stu-dent’s t” and 00350D, “Improved Normal and Inverse Distribution.” For values at
other than the 95 % probability level, see published tables of critical values of
Student’s t in any standard statistical text Further use of this table is defined in
Practice D2905
Trang 410.7 Unless otherwise specified, measure the elongation of
the fabric at any stated load by means of a suitable autographic
recording device, at the same time the breaking strength is
determined Measure the elongation from the point where the
curve leaves the zero loading axis to a point of corresponding
force in millimetres [inches]
11 Calculation
11.1 Breaking Load—Calculate the breaking load by
aver-aging the value of breaking load for all accepted specimen
results The breaking load shall be determined separately for
the machine direction specimens and cross-machine direction
specimens
11.2 Apparent Elongation—Calculate the apparent
elonga-tion at the breaking load or at other specified loads by
averaging the values of apparent elongation for all accepted
specimen results The apparent elongation shall be determined
separately for the machine direction specimens and
cross-machine direction specimens and expressed as the percentage
increase in length, based upon the initial nominal gage length
of the specimen Report this as the apparent elongation
N OTE 4—The observed elongation calculated as a percentage of the
initial nominal gage length of the specimen should be referred to as
“apparent elongation.” Because the actual length of fabric stretched is
usually somewhat greater than this initial length due to pull-out of fabric
from between the jaws, elongation calculated on initial length may be
somewhat in error, depending upon the amount of this pull-out.
12 Report
12.1 Report the following information:
12.1.1 State that the tests were performed as directed in Test
Method D4632/D4632M Describe the material(s) or
prod-uct(s) sampled and the method of sampling used
12.1.2 The average grab breaking load for specimens cut in
each direction, for all specimens giving acceptable breaks
12.1.3 The average grab percent apparent elongation of
specimens cut in each direction, for all specimens giving
acceptable breaks, if required Identify this as “apparent
breaking elongation,” or “apparent elongation at x lb load,” as
required by the test specifications
12.1.4 Number of specimens tested in each direction
12.1.5 Condition of specimens (wet or dry)
12.1.6 Type of testing machine used
12.1.7 Maximum load obtainable in the range used for
testing
12.1.8 Type of padding used in jaws, modification of specimen gripped in the jaws, or modification of jaw faces, if used
12.1.9 Any modifications of sample specimens as manufactured, or test method as described
13 Precision and Bias 4
13.1 Precision—The precision of this test method is based
on an interlaboratory study of D4632/D4632M, Standard Test Method for Grab Breaking Load and Elongation of Geotextiles, conducted in 2013 Ten laboratories tested a total
of four different geotextile samples for elongation and tensile strength at rupture Every “test result” represents an individual determination All labs were asked to report triplicate test results for each material tested PracticeE691was followed for the design and analysis of the data; the details are given in ASTM Research Report No RR:D35-1021
13.1.1 Repeatability Limit (r)—Two test results obtained
within one laboratory shall be judged not equivalent if they differ by more than the “r” value for that material; “r” is the interval representing the critical difference between two test results for the same material, obtained by the same operator using the same equipment on the same day in the same laboratory
13.1.1.1 Repeatability limits are listed inTables 2 and 3
13.1.2 Reproducibility limit (R)—Two test results shall be
judged not equivalent if they differ by more than the “R” value for that material; “R” is the interval representing the critical difference between two test results for the same material, obtained by different operators using different equipment in different laboratories
13.1.2.1 Reproducibility limits are listed inTables 2 and 3 13.1.3 The above terms (repeatability limit and reproduc-ibility limit) are used as specified in Practice E177
13.1.4 Any judgment in accordance with statements13.1.1 and 13.1.2 would have an approximate 95 % probability of being correct
13.2 Bias—At the time of the study, there was no accepted
reference material suitable for determining the bias for this test method, therefore no statement on bias is being made
4 Supporting data have been filed at ASTM International Headquarters and may
be obtained by requesting Research Report RR:D35-1021 Contact ASTM Customer Service at service@astm.org.
TABLE 2 Maximum Elongation at Rupture (%)
Repeatability Standard Deviation
Reproducibility Standard Deviation
Repeatability Limit Reproducibility Limit
Woven Slit Tape
Stabilization Geotextile
Heavy Weight
Nonwoven Geotextile
Light Weight
Nonwoven Geotextile
Woven Mono/Slit Tape
Reinforcement Geotextile
A
The average of the laboratories’ calculated averages.
Trang 513.3 The precision statement was determined through
sta-tistical examination of 240 reported results, from ten
laboratories, on four materials These four materials were
identified as the following:
Woven Slit Tape Stabilization Geotextile
Light Weight Nonwoven Geotextile
Heavy Weight Nonwoven Geotextile
Woven Mono/Slit Tape Reinforcement Geotextile
13.4 To judge the equivalency of two test results, it is recommended to choose the material closest in characteristics
to the test material
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TABLE 3 Maximum Tensile at Rupture (lbf)
Repeatability Standard Deviation
Reproducibility Standard Deviation
Repeatability Limit Reproducibility Limit
Woven Slit Tape
Stabilization Geotextile
Light Weight
Nonwoven Geotextile
Heavy Weight
Nonwoven Geotextile
Woven Mono/Slit Tape
Reinforcement Geotextile
A
The average of the laboratories’ calculated averages.